Human apolipoprotein A4 (APOA4), a 46 kDa exchangeable class A apolipoprotein predominantly synthesized in small intestinal enterocytes, distributes across triglyceride-rich chylomicrons, high-density lipoprotein (HDL) particles, and circulating lipoprotein-free plasma fractions. Structurally defined by tandem amphipathic α-helical repeat domains, it mediates reverse cholesterol transport, activates lecithin-cholesterol acyltransferase, governs postprandial lipid and glucose homeostasis, and suppresses vascular oxidative stress, exerting potent anti-atherosclerotic and endothelial-protective bioactivities. APOA4 interacts with apolipoprotein A2 (APOA2) via helical domain association on HDL surfaces; they co-assemble into lipoprotein complexes and share endothelial binding sites, jointly modulating HDL structural stability and metabolic turnover.
Thus a functional ELISA assay was conducted to detect the interaction of recombinant APOA4 and recombinant APOA2. Briefly, APOA4 was diluted serially in PBS with 0.01% BSA (pH 7.4). Duplicate samples of 100 μL were then transferred to APOA2-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-APOA4 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody for 1h at 37℃, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 μL stop solution to the wells and read at 450/630nm immediately. The binding activity of recombinant APOA4 and recombinant APOA2 was shown in Figure 1, the EC50?for this effect is 0.142 μg/mL.